Barbershopvocal harmony, as codified during the barbershop revival era (1930s–present), is a style of a cappella, or unaccompanied vocal music, characterized by consonant four-part chords for every melody note in a predominantly homophonic texture. Each of the four parts has its own role: generally, the lead sings the melody, the tenor harmonizes above the melody, the bass sings the lowest harmonizing notes, and the baritone completes the chord, usually below the lead. The melody is not usually sung by the tenor or baritone, except for an infrequent note or two to avoid awkward voice leading, in tags or codas, or when some appropriate embellishment can be created. Occasional passages may be sung by fewer than four voice parts.

According to the Barbershop Harmony Society (BHS), "Barbershop music features songs with understandable lyrics and easily singable melodies, whose tones clearly define a tonal center and imply major and minor chords and barbershop (dominant and secondary dominant) seventh chords that resolve primarily around the circle of fifths, while making frequent use of other resolutions."[1] Slower barbershop songs, especially ballads, often eschew a continuous beat, and notes are often held (or sped up) ad libitum.

With the exception of the bass, the voice parts in barbershop singing do not correspond closely to their classical music counterparts; the tenor range and tessitura are similar to those of the classical countertenor, the baritone resembles the Heldentenor or lyric baritone in range and a tenor in tessitura, and the lead generally corresponds to the tenor of classical repertoire, with some singers possessing a tessitura more similar to that of a high baritone. Barbershop singing is performed both by men's and women's groups; the elements of the barbershop style and the names of the voice parts are the same for both (although women's groups generally have a different standing arrangement than their male counterparts).

The defining characteristic of the barbershop style is the ringing chord. This is a name for one specific and well-defined acoustical effect, also referred to as expanded sound,the angel's voice,the fifth voice, the overtone, or barbershop seventh. (The barbershopper's "overtone" is the same as the acoustic physicist's overtone or harmonic, although the numbers differ. The first overtone, at twice the fundamental frequency, is the second harmonic, etc. The undertone is the difference between the frequencies of two sung notes and is known as heterodyning).

The physics and psychophysics of the effect are fairly well understood; it occurs when the upper harmonics in the individual voice notes, and the sum and difference frequencies resulting from nonlinear combinations within the ear, reinforce each other at a particular frequency, strengthening it so that it stands out separately above the blended sound. The effect is audible only on certain kinds of chords, and only when all voices are equally rich in harmonics and justly tuned and balanced. It is not heard in chords sounded on modern keyboard instruments, due to the slight tuning imperfection of the equal-tempered scale.

Gage Averill writes that "Barbershoppers have become partisans of this acoustic phenomenon" and that "the more experienced singers of the barbershop revival (at least after 1938) have self-consciously tuned their dominant seventh and tonic chords in just intonation to maximize the overlap of common overtones." However, "In practice, it seems that most leads rely on an approximation of an equal-tempered scale for the melody, to which the other voices adjust vertically in just intonation."[2]

What is prized is not so much the "overtone" itself, but a unique sound whose achievement is most easily recognized by the presence of the "overtone". The precise synchrony of the waveforms of the four voices simultaneously creates the perception of a "fifth voice" while at the same time melding the four voices into a unified sound. The ringing chord is qualitatively different in sound from an ordinary musical chord e.g. as sounded on a tempered-scale keyboard instrument.

Most elements of the "revivalist" style are related to the desire to produce these ringing chords. Performance is a cappella to prevent the distracting introduction of equal-tempered intonation, and because listening to anything but the other three voices interferes with a performer's ability to tune with the precision required. Barbershop arrangements stress chords and chord progressions that favor "ringing", at the expense of suspended and diminished chords and other harmonic vocabulary of the ragtime and jazz forms.

The dominant seventh-type chord is so important to barbershop harmony that it is called the "barbershop seventh". BHS arrangers believe that a song should contain dominant seventh chords anywhere from 35 to 60 percent of the time (measured as a percentage of the duration of the song rather than a percentage of the chords present) to sound "barbershop".

Historically barbershoppers may have used the word "minor chord" in a way that is confusing to those with musical training. Averill suggests that it was "a shorthand for chord types other than major triads", and says that the use of the word for "dominant seventh-type chords and diminished chords" was common in the late nineteenth century. A 1910 song called "Play That Barber Shop Chord"[3] (often cited as an early example of "barbershop" in reference to music) contains the lines:

'Cause Mister when you start that minor part
I feel your fingers slipping and a grasping at my heart,
Oh Lord play that Barber shop chord!

Averill notes the hints of rapture, "quasi-religion" and erotic passion in the language used by barbershoppers to describe the emotional effect. He quotes Jim Ewin as reporting "a tingling of the spine, the raising of the hairs on the back of the neck, the spontaneous arrival of goose flesh on the forearm ... the fifth note has almost mysterious propensities. It's the consummation devoutly wished by those of us who love Barbershop harmony. If you ask us to explain why we love it so, we are hard put to answer; that's where our faith takes over." Averill notes too the use of the language of addiction, "there's this great big chord that gets people hooked." An early manual was entitled "A Handbook for Adeline Addicts".[2]

He notes too that "barbershoppers almost never speak of 'singing' a chord, but almost always draw on a discourse of physical work and exertion; thus, they 'hit', 'chop', 'ring', 'crack', 'swipe', and 'bust.' Vocal harmony is interpreted as an embodied musicking. Barbershoppers never lose sight (or sound) of its physicality."[2]

In the last half of the 19th century, U.S. barbershops often served as community centers, where most men would gather. Barbershop quartets originated with African American men socializing in barbershops; they would harmonize while waiting their turn, vocalizing in spirituals, folk songs and popular songs. This generated a new style, consisting of unaccompanied, four-part, close-harmony singing. Later, white minstrel singers adopted the style, and in the early days of the recording industry their performances were recorded and sold. Early standards included songs such as "Shine On, Harvest Moon", "Hello, Ma Baby", and "Sweet Adeline". Barbershop music was very popular between 1900 and 1919 but gradually faded into obscurity in the 1920s. Barbershop harmonies remain in evidence in the a cappella music of the black church.[4][5][6] The iconic barbershop quartets are typically dressed in bright colors, boaters and vertical stripe vests, though costuming and attire can vary.[7]

The revival of a cappella singing took place around 1938 when a tax lawyer named Owen C. Cash sought to save the art form from a threat by radio.[8] He garnered support from an investment banker named Rupert I. Hall. Both came from Tulsa, Oklahoma.[9] Cash was a true partisan of quartet singing who advertised the fact that he did not want a cappella to fall by the wayside.

Cash had struck a chord, albeit unwittingly, and soon, across North America, men responded in their thousands and later in the same year the "Society for the Preservation and Encouragement of Barber Shop Quartet Singing in America" was set up, known by the abbreviation S.P.E.B.S.Q.S.A.[10] at a time when many institutions in the United States were in the habit of using multiple initials to denote their function. The group adopted the alternate name "Barbershop Harmony Society" early in its history. While its legal name has never changed, it changed its official brand name to "Barbershop Harmony Society" in 2004.

Sharp Harmony, a Norman Rockwell painting, appeared on the cover of The Saturday Evening Post magazine issue dated September 26, 1936; it depicts a barber and three clients enjoying an a cappella song. The image was adopted by SPEBSQSA in its promotion of the art.

Traditionally, the word "barbershop" has been used to encompass both men's and women's quartets singing in the barbershop style. Harmony, Inc. calls itself "International Organization of Women Barbershop Singers" while Sweet Adelines International calls itself "a worldwide organization of women singers committed to advancing the musical art form of barbershop harmony."

In North America most male barbershop quartet singers belong to the Barbershop Harmony Society,[citation needed] while most female barbershop quartet singers are in either Sweet Adelines International or Harmony, Inc.[citation needed] Similar organizations have sprung up in many other countries.

Most barbershop quartet singers also choose to sing in a chorus.[citation needed]

A barbershop chorus sings a cappella music in the barbershop style. Most barbershop choruses belong to a larger association of practitioners such as the Barbershop Harmony Society, Sweet Adelines International or Harmony, Inc.[citation needed]

In the Barbershop Harmony Society, a chorus is the main performing aspect of each chapter. Choruses may have as few as 12 or as many as 150 members singing. Choruses normally sing with a director, as distinct from quartets. It is not uncommon for a new quartet to form within a chorus, or for an established quartet affiliated with a given chorus to lose a member (to death, retirement, or relocation) and recruit a replacement from the ranks of the chorus. Choruses can also provide "spare parts" to temporarily replace a quartet member who is ill or temporarily out of town.

Unlike a quartet, a chorus need not have equal numbers singing each voice part. The ideal balance in a chorus is about 40% bass, 30% lead, 20% baritone and 10% tenor singers.

Filling the gap between the chorus and the quartet is what is known as a VLQ or Very Large Quartet, in which more than four singers perform together, with two or more voices on some or all of the four parts. A VLQ possesses greater flexibility than a standard quartet, since they can perform even with one or more singers missing, as long as all four parts are covered. Like a normal quartet, a VLQ usually performs without a director.

The Great Western Chorus of Bristol: winners of a record eight gold medals (1977, 1980, 1981, 1983, 1990, 2008 and 2010); four times BABS silver medalists and five times bronze medalists. The Great Western Chorus hold more chorus competition medals than any other chorus in the association; Radio 3 "Choir of the Year" 2006 Finalists; based in Bristol, England. Won the inaugural Barnardo's Adult Male Choir Competition. Always placed within top five nationally.

Mantunian Way: a youth chorus from the University of Manchester; part of the Manchester University Barbershop Singers (MUBS); the association's first and so far only full youth chorus (in which all members and committee members are under 26 years of age); 2014 British Bronze Medalist Chorus; the first youth chorus to win national medalist ranking and the first chorus in the association's history to win a medal in their national contest debut.[citation needed]

While these traditional songs still play a part in barbershop today, barbershop music also includes more current titles. Most music can be arranged in the barbershop style, and there are many arrangers within the aforementioned societies with the skills to include the barbershop chord structure in their arrangements. Today's barbershop quartets and choruses sing a variety of music from all eras—show tunes, pop, and even rock music has been arranged for choruses and quartets, making them more attractive to younger singers.

^Abbott, Lynn (1992). "Play That Barber Shop Chord: A Case for the African American Origin of Barbershop Harmony". American Music (University of Illinois Press) 10 (3): 289–325. doi:10.2307/3051597. JSTOR3051597.

^Henry, James Earl (2000). The Origins of Barbershop Harmony: A Study of Barbershop's Links to Other African American Musics as Evidenced through Recordings and Arrangements of Early Black and White Quartets. Washington University.

^"In Harmony" (139). Barbershop Harmony Australia. November–December 2013. p. 12. In their debut Convention performance, third place bronze medal chorus was won by Sound Connection with a score of 76.4%